Bushing systems in prior art doors for insulated steel shell safes suffer from a number of disadvantages, but must be used to support rotatable components such as combination locks, key-operated locks, and handles. All of these components are accessed from outside the safe, rotate, and interact with additional components on the inner surface of the door. Components such as locks and handles each have one or more parts on the exterior of the door attached to a rotatable spindle extending through the door, the spindle also being attached to additional components on the interior of the door. The bushing system allows rotation of the spindles; provides support for the spindles and other components; and allows the spindles to pass through the door's front plate, insulation and jamb. In addition, the bushing system typically serves as a mount for internal components of the safe, such as tumbler discs or live bolt drivers.
Prior art bushing systems generally use individual bushings installed during assembly of the door. Each bushing comprises a series of parts that must themselves be assembled during installation. A prior art bushing assembly typically comprises a metal or resin tube through which a spindle passes. The tube passes through the door and is flanged on each end or otherwise secured to prevent longitudinal motion of the tube. The spindle is attached to a knob or handle at one end and a driver for internal safe components at the other end. A stub is mounted about the inner or rearward end of the tube and supports rotatable internal components of the safe, such as tumbler discs of a combination lock. The stub is held in place by a flange or the like extending into the insulation of the safe door as well as a shoulder bearing on the inner surface of the door. Alternatively, a plate attached to the stub screws into the inner or rearward surface of the safe door, allowing alignment adjustment by shimming of the plate. Another system includes a disc spring that allows the bushing to be somewhat out of alignment without interfering with operation of the rotatable components.
One disadvantage of conventional bushing systems is the difficulty of aligning and orienting all the bushing parts. This is especially true of post-pour installation of bushings in doors using concrete insulation, since precise alignment of a drill during boring of holes through concrete is often difficult to achieve. While some prior art systems allow adjustment of bushing alignment or tolerate some misalignment, there is a need for a bushing system that provides proper alignment and orientation of the bushings more consistently than conventional bushing systems.
A contributing factor to the bushing alignment problem is the number of parts in prior art bushing systems. Each part that must be installed is a source of alignment error and adds to installation duration. Thus, there is also a need for bushing systems with fewer parts to reduce alignment errors and installation time.
An additional disadvantage of conventional bushing systems that include metal pass-through tubes is heat conduction into the interior of the safe. While less heat-conductive bushing systems are in existence, there is still a need for bushing systems with reduced heat conduction into safe interiors. Thus, there is a need for a bushing system that is more consistently and easily aligned, has fewer parts, and conducts less heat than prior art bushing systems.